chore: add autofill-problem-readme copilot prompt

Author: scarowar

prompts/autofill-problem-readme.txt

@@ -0,0 +1,7 @@
+Fill out the following #file:README.md for the given LeetCode problem:
+
+- Reference the provided #file:solution.py implementation.
+- For each section (Intuition, Approach, Complexity, Notes), write content that is concise, precise, and highly impactful—ideal for quick revision and long-term recall.
+- Use clear language that would help in recalling it easily.
+- Limit each section to 1–2 sentences.
+- In the Notes section, mention any common alternative solutions, edge cases, or key insights in a single line.